TWI694672B - Speed control system of general motor - Google Patents

Abstract

A speed control system of a universal motor, which is electrically connected to a universal motor, and includes a speed detection unit and a controller, the controller is provided with a slow start unit, a speed control unit and a blocking protection unit , The slow-start unit enables the speed of the general-purpose motor to rise smoothly. The speed control unit controls and compensates the speed of the general-purpose motor in a closed-loop manner to achieve the effect of stepless speed regulation. When used at low speed, it has a high speed Approximate cutting capacity at speed, the blocking protection unit can automatically power off for protection when the machine is blocked.

Description

Speed control system of general motor

The invention relates to a speed control system, especially a speed control system of a general motor.

Press, the rotor and stator of the conventional universal motor are wound around the armature, and the two are connected by the carbon brush and the commutator, so that it achieves the effect of automatic commutation during operation, just input the general household AC power to make The motor is running, because of the low price and simple control, it is widely used in hand tools and small household tools. In order to reduce the size of the motor, the motor body with a high speed is generally used on the market with a reduction gear box. The huge noise and speed generated during high-speed operation are easily lost due to voltage fluctuations. And the general motor adopts a simple speed control device, which cannot achieve constant speed control. Because its control method is to limit the conduction angle of the AC voltage, the torque of the motor is also reduced at low speed, which is not suitable for use in a high-load environment. The general motor will generate a large starting current at the moment of starting, and the motor body will also violently vibrate, which seriously affects the life and stability of the machine. Therefore, there are still many shortcomings. It is not a good design and needs to be improved urgently. Therefore, after observing the above shortcomings, the creator of this case believes that the conventional general-purpose motor is necessary for improvement, and the invention has been produced.

The purpose of the present invention is to provide a speed control system for a general-purpose motor, which enables the speed of the general-purpose motor to rise steadily when starting, automatically corrects the difference in speed, has the stability effect of stepless speed regulation, and when used at low speed, It has a cutting capacity similar to that at high speed.

In order to achieve the above purpose, the speed control system of a general-purpose motor provided by the present invention is electrically connected to a general-purpose motor, and includes: a speed detection unit, which is provided in the general-purpose motor; and a controller, It is electrically connected to the universal motor and the speed detection unit. The controller has a slow start unit, a speed control unit, and a blocking protection unit. The slow start unit has a start flag initial mode Group and a start flag removal module, the start flag initial module has a start flag and an independent acceleration weight, the speed control unit has a speed command input module, a calculation module and a compensation Module, the blocking protection unit is electrically connected to the speed detection unit.

The speed control system of the universal motor provided by the present invention, when the universal motor is started, the startup flag initial module initializes the startup flag and the acceleration weight, the acceleration weight is an independent acceleration value, And the rotation speed of the general motor can be increased smoothly. When the rotation speed of the general motor rises to the set reference value, the start flag clearing module will clear the start flag and cut off the slow start unit to enter the The speed adjustment process of the speed control unit uses the speed command input module to issue a speed command to control the running speed of the general motor. The calculation module calculates the general motor according to the signal frequency fed back by the speed detection unit The actual speed, and the actual speed minus the speed command to calculate a speed difference to determine the correction amount required for the conduction angle. The compensation module compensates the conduction angle value based on the correction amount to achieve the effect of adjusting the speed. When the general motor is running, when the blocking protection unit calculates the actual speed of the general motor is too low or stops according to the signal frequency fed back by the speed detection unit, the blocking protection unit will send a protection signal to pass The electromagnetic switch cuts off the power supply to achieve a protective effect, whereby the slow start unit enables the speed of the universal motor to be smoothly increased To improve the violent vibration of starting the machine, and then the speed control unit automatically corrects the speed difference, which has the stability effect of stepless speed regulation. When used at low speed, it has a cutting capacity similar to that at high speed. When the machine is blocked, the blocking protection unit can automatically power off for protection, increasing the safety and service life of the machine.

100: Speed control system of general motor

10: General motor

11: Machine

12: Electromagnetic switch

13: Power

20: Speed detection unit

30: Controller

31: Slow start unit

311: Start flag initial module

312: Start flag clearing module

313: Start flag

32: Speed control unit

321: AC zero crossing detection module

322: Speed command input module

323: Computing module

324: compensation module

33: Block the protection unit

Figure 1 is a system block diagram of the preferred embodiment of the present invention.

Figure 2 is a perspective view of the machine of the present invention.

Figure 3 is a flowchart of the steps of the slow start of the preferred embodiment of the present invention.

Figure 4 is a flow chart of the steps of speed control according to the preferred embodiment of the present invention.

FIG. 5 is a schematic diagram of detecting the AC zero crossing position according to the preferred embodiment of the present invention.

Figure 6 is a schematic diagram of the compensation module controlling the opening and closing time according to the preferred embodiment of the present invention.

Figure 7 is a schematic diagram of the compensation module controlling the opening and closing time according to the preferred embodiment of the present invention.

Please refer to FIG. 1, FIG. 2 and FIG. 3, which is a system block diagram and a machine perspective view of a preferred embodiment of the present invention, which discloses a universal motor speed control system 100, whose electrical phase Connected to a universal motor 10, the universal motor 10 can be installed on a machine 11, the machine 11 is electrically connected to a power supply 13 by an electromagnetic switch 12, the speed control system 100 of the universal motor includes: A speed detection unit 20 is provided in the universal motor 10, and the speed detection unit 20 is a Hall element.

A controller 30 is electrically connected to the universal motor 10 and the speed detection unit 20. The controller has a slow start unit 31, a speed control unit 32, and a blocking protection unit 33.

The slow start unit 31 has a start flag initial module 311 and a start flag clear module 312, the start flag initial module 311 has a start flag 313 and an independent acceleration weight, please refer to As shown in FIG. 3, when the universal motor 10 is started, the start flag initial module 311 initializes the start flag 313 and the acceleration weight. The acceleration weight is an independent acceleration value, so that the The rotation speed of the general motor 10 can rise smoothly. When the rotation speed of the general motor 10 rises to the set reference value, the start flag clearing module 312 will clear the start flag 313 and cut off the slow start unit 31. Enter the speed adjustment flow of the speed control unit 32.

The speed control unit 32 has an AC zero-crossing detection module 321, a speed command input module 322, a calculation module 323, and a compensation module 324 electrically connected, please refer to FIG. 4 As shown, the AC zero-crossing detection module 321 uses a hardware circuit to detect the position P of the zero-crossing point of the AC power supply. As shown in FIG. 5, in the embodiment of the present invention, the resistance and Nano-diodes form a circuit that converts the AC sine wave voltage signal into a DC square wave digital signal synchronized with AC, which can provide the AC zero-crossing point position P to the speed control unit 32 for use as a reference point for speed control. The speed command input module 322 uses a variable resistor to issue a speed command in an analog signal manner, such as a speed control knob to control the operating speed of the universal motor 10, and the calculation module 323 is based on the speed detection unit The signal frequency of 20 feedbacks calculates the actual speed of the universal motor 10, and subtracts the speed command to calculate a speed difference, and uses the speed difference to calculate the speed compensation. In the embodiment of the present invention, when the actual speed is greater than the speed When commanding, the speed difference is brought into the following equation to calculate the required conduction angle θ value and the cut-off time (Delay value) required to maintain the speed, where u is the speed control output signal and K _p is Proportional gain, K _i is the integral gain, e is the speed difference, t is the time, and τ is the integral variable. The compensation module 324 uses the TRIAC (triac) to control the conduction angle and cut-off time of the compensation The opening and closing time cuts off a part of the complete AC voltage sine wave waveform, as shown in Figures 6 and 7, for example, the calculation module 323 is used to calculate the conduction angle and cutoff required by the general motor 10 to maintain the speed Time, with the measured speed feedback signal, the cut-off time is adjusted and corrected, which is the speed compensation, so that the overall voltage supplied to the motor drops to achieve the effect of speed reduction for control, when the actual speed is less than the speed command The compensation module 324 can increase the running speed of the universal motor 10 to meet the speed command. In this way, the speed control unit of the present invention adjusts and corrects the cut-off time with the measured speed feedback signal in a closed-loop speed control mode, which is speed compensation, and achieves the effect of speed adjustment.

The equation u ( t )= K _p e ( t )+ K _i ∫ ₀ ^t e ( τ ) dτ .

The blocking protection unit 33 is electrically connected to the speed detection unit 20 and the electromagnetic switch 12. When the blocking protection unit 33 calculates the universal motor according to the signal frequency fed back by the speed detection unit 20 When the actual speed of 10 is too low or stops, the blocking protection unit 33 will send out a protection signal to cut off the power supply 13 through the electromagnetic switch 12 to achieve protection.

In order to further understand the structural features of the present invention, the use of technical means and the expected effect, the use of the present invention is described here. I believe that I can have a deeper and more specific understanding of the present invention as follows: please continue to refer to As shown in FIG. 2 and FIG. 3, in the embodiment of the present invention, the machine 11 is a circular saw machine, and the universal motor 10 is an AC brush motor. When the machine 11 is started, the start flag initial mode Group 311 initializes the start flag 313 and the acceleration weight. The acceleration weight is an independent acceleration value, so that the speed of the universal motor 10 can rise smoothly. The speed detection unit 20 The actual speed of the general-purpose motor 10 is calculated according to the feedback signal frequency. The start flag initial module 311 determines whether the actual speed of the general-purpose motor 10 reaches the reference value. If the reference speed is not reached, the start flag The initial module 311 maintains the start flag 313 and continues to increase the speed of the general motor 10 with the acceleration weight. When the speed of the general motor 10 increases to the set reference value, the start flag clearing module 312 becomes The start flag 313 is cleared, and the slow start unit 31 is cut off to enter the speed control process of the speed control unit 32. When the present invention is actually used, the peak value of the measured current is reduced to 28 A, which is 83 A relative to the peak value when the slow start unit 31 is not installed, so the starting current is reduced by about 2/3, and the drastic start of the machine is improved. Shock situation.

Please continue to refer to FIG. 4 and FIG. 5 to proceed with the speed control process. The speed control unit 32 will first use the AC zero-crossing detection module 321 to detect the AC zero-crossing position P with a hardware circuit As a reference point for speed control, the user can then issue the speed command from the speed command input module 322, and the calculation module 323 then calculates the actual speed of the universal motor 10 according to the feedback of the speed detection unit 32 , And the actual speed is subtracted from the speed command to calculate the speed difference, then the equation u ( t ) can be used to calculate the correction value for the conduction angle and the cut-off time, and finally the compensation module 324 is used to control the opening and closing time to achieve The effect of adjusting the speed. In this way, the present invention adopts closed-loop speed control, so the speed difference can be automatically corrected, the speed error is maintained within 50 rpm, and the stability effect of stepless speed regulation can be achieved from 2000 rpm to 4000 rpm. Moreover, when the present invention is used at a low speed, for example, after the saw blade reduces the rotational speed due to contact with the load, the compensation module 324 can increase the torque to a cutting capacity similar to that at high rotational speed, thereby making the low rotational speed have low noise and save Electricity and cutting ability similar to high-speed state, and in the low-speed state, the saw blade can be replaced with a grinding wheel blade for grinding, which achieves the universality of one machine and two uses.

Finally, in the present invention, the saw blade is blocked with wood during the operation of the machine 11, and the blocking protection unit 33 is actually tested. After the machine 11 detects an abnormality, the protection signal is sent to automatically use the electromagnetic switch 12 For power-off protection, the user manually turns on the power of the machine 11 after eliminating the abnormality, and the machine 11 can still be used normally, thereby increasing safety and service life.

Hereafter, the characteristics of the present invention and the achievable expected effects are stated as follows: The speed control system of the general-purpose motor provided by the present invention, the slow-start unit 31 first enables the speed of the general-purpose motor 10 to rise smoothly to improve the start In the case of severe vibration of the machine 10, the speed control unit 32 automatically corrects the difference in speed. When used at low speed, it has a cutting capacity similar to that at high speed. It can also be replaced with a grinding wheel for grinding to increase the machine. The stability and versatility of 11, when the machine 11 is finally blocked, the blocking protection unit 33 can be automatically powered off for protection, increasing the safety and service life of the machine.

In summary, the present invention has its excellent progress and practicality in similar products. At the same time, it has searched the technical information about this kind of structure at home and abroad, and the same structure has not been found in the literature. Therefore, The present invention already possesses the essentials of the invention patent, and the application is filed according to law.

However, the above is only one of the preferred and feasible embodiments of the present invention. Therefore, any equivalent structural changes that apply to the description of the present invention and the scope of patent application should be included in the patent scope of the present invention.

100: Speed control system of general motor

10: General motor

12: Electromagnetic switch

20: Speed detection unit

30: Controller

31: Slow start unit

311: Start flag initial module

312: Start flag clearing module

313: Start flag

32: Speed control unit

321: AC zero crossing detection module

322: Speed command input module

323: Computing module

324: compensation module

33: Block the protection unit

Claims (6)

A speed control system of a general-purpose motor, which is electrically connected to a general-purpose motor, and includes: a speed detection unit, which is provided on the general-purpose motor; and a controller, which is connected with the general-purpose motor and the speed detection The measuring unit is electrically connected, the controller has a slow start unit, a speed control unit and a blocking protection unit, the slow start unit has a start flag initial module and a start flag clear module, The start flag initial module has a start flag and an independent acceleration weight. When the speed of the universal motor is increased to the set reference value, the start flag clear module will clear the start flag. The speed control unit has a speed command input module, a calculation module and a compensation module. The calculation module calculates the actual speed of the universal motor according to the signal frequency fed back by the speed detection unit, and A speed difference is calculated by subtracting a speed command from the actual speed to determine the correction amount required for the conduction angle. The compensation module compensates for the correction amount. The blocking protection unit and the speed detection unit and an electromagnetic switch When the blocking protection unit calculates the actual speed of the universal motor is too low or stops according to the signal frequency fed back by the speed detection unit, the blocking protection unit will send a protection signal to pass The electromagnetic switch cuts off the power supply of the universal motor. According to the speed control system of the universal motor described in item 1 of the patent application, wherein the speed control unit has an AC zero-crossing detection module, the AC zero-crossing detection module detects AC power The position of the zero crossing point is used as the reference point for speed control. According to the speed control system of the general-purpose motor described in item 2 of the patent application scope, in which the calculation module brings the speed difference into the equation u ( t ) = K _p e ( t ) + K _i ∫ ₀ ^t e ( τ ) In dτ , where u is the speed control output signal, K _p is the proportional gain, K _i is the integral gain, e is the speed difference, t is the time, and τ is the integral variable to calculate the conduction angle value to be compensated To determine the amount of correction required for the conduction angle. According to the speed control system of the general-purpose motor described in Item 3 of the patent application range, the compensation module uses TRIAC (triac) to control the opening and closing time of the conduction angle value to be compensated. According to the speed control system of the general-purpose motor described in item 1 of the patent application range, the speed control unit is a closed-loop speed control. According to the speed control system of the universal motor described in item 1 of the patent application scope, wherein the speed detection unit is a Hall element.

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